Friday, 31 August 2012

The repaired Hazel bow has now had a total of over 300 arrows shot through it and is finally declared finished, it's drawing about 43# at 28" and sweet as a nut.
Thinking of Hazel turned my mind to the bow I made in a day at the club back in May http://bowyersdiary.blogspot.co.uk/2012/05/woodland-workshop.html
It had already had a few minor improvements but was still a bit of a pig to shoot, the grip being as wide as the Mississippi and as uncomfortable as a 3 hour flight with a budget airline.
I had some Hazel off cuts from the same tree so I glued a piece onto the belly side of the grip with the curve of the grain rings matching up. I sculpted the grip to be centre shot and as skinny as I dared.
It now shoots clean and true even with my 100gn arrows which used to be too stiff for it. I checked it on the tiller and its a tad over 30# at 28".

I slimmed the tips down considerably to remove excess weight which helps keep the speed up.

I might take it to the village fete near the club on Sunday where we are doing a have-a-go.

Meanwhile the Maple bow has been worked down so it's just beginning to flex on the tiller, I should have some pics over the weekend. I've been taking rough thickness measurements from the Hazel bow to get me to the current state, obviously adding a mm or two to stay on the safe side. That's the great thing about having experience and a dozen bows lying around, you always have some sort of reference. I'll make it as long as that one, with tips like that one, and a grip like t'other.

Tuesday, 28 August 2012

I got home from work and shot the last 10 arrows to make up the 100 through the Hazel bow. Running my fingers over the back, it just didn't feel as smooth as it should. There wasn't actually a lift at the splinter, but it didn't feel right.
I winched it back to 28" on the tiller and felt it again with my thumb nail, I could just feel the slightest edge.
It's almost a relief to make the decision to patch it.
The problem with a splinter or a split is you can never get glue down into the root of the crack, and if you prise open the crack to gain access it just makes it travel further down into the wood.
I set about chiseling out the splinter using a ground down needle file which was a bit too flexible and then I remembered my plough plane which has some narrow blades, one of which was just the job.
I was getting slightly anxious that I hadn't uncovered the root of the splinter, then, as I was cleaning out the base of the channel I could see a wafer thin remnant of the splinter lifting, (see pic top right).

Once the groove was cleaned and straightened using the edge of a file I sawed a thin sliver to fill it in. I'd kept the scrap pieces from where I'd roughed the bow out on the bandsaw, and one of these was soon shaped to suit, using bandsaw, spokeshave to curve it slightly and sand paper. I glued it in using Resintite and whilst pressing it firmly in place rasped off some of the excess so that it would be more flexible and would pull down into the contour of the groove better when I bound it with rubber strapping.

You can see how narrow and shallow the groove is, I'm pretty convinced that it's mostly cosmetic and feel that I could have strung the bow and shot it with the cleaned out groove. I didn't of course as that would simply be foolhardy.
We'll see how it looks tomorrow night.

Update:-
Two more pics, first with the wrapping removed, and the second with it cleaned and polished. You can see how the repair runs right through the area with the tiny pin knots.
The inlaid section fits better near the grip, but I was keen to make sure it pressed in right to the bottom of the groove so I didn't make it too tight a fit.

It doesn't look much worse than the original splinter.

I've shot 10 arrows through it and had it up on the tiller. Looking good, I'll be happy once I've shot another 90.

Monday, 27 August 2012

I'm starting on a Maple primitive, along similar lines to the Hazel (which is looking good having shot another 30 through it). It will be interesting to compare the two.
I've used Maple from the same woodland before for a stupidly long longbow and an under powered American Flatbow. I'm hoping that the primitive shape will suit the wood better, but I feel I may need to heat treat the belly to get the best from it.

A youngish chap and his dad visited me to chat about longbows, he was about to start university studying History. I was slightly nonplussed, as despite my great age, I don't actually know firsthand much about the military use of the longbow. I stressed the difference between the few facts we know and the interpretation thereof. He was pleased that my suppositions about Agincourt agreed with his.
We had a good go with my bows and he felt the Yew with a spokeshave. There is a big difference between reading about heartwood and sapwood and actually feeling it.
I let him split one half of my big Maple log with axe and wedges. Again, it's something which, until you try it you have no idea of. The Maple split easily and illustrated nicely how there is no need for bandsaws and modern machinery.

One of the bit I like best was how impressed they were with the speed of draw and loose, having seen Olympic archers holding at full draw for over 10 seconds. the speed of the arrow and the fact that it hit what was aimed at was pretty good too. The good old Chinese Repeating Crossbow also got it's customary outing and was an interesting juxtaposition to the old soundbite that 'The Longbow was the machine gun of the middleages' which is far from accurate, but has an small element of truth.
It's not easy to put the position of the Longbow into a soundbite, as without the manpower, training, organisation and supply it is just a stick.
The mobilisation of a well drilled, well suppied, well disciplined army is what allowed us to win, but even that would have come to nothing if the French had been organised and used their resources wisely.
(Just my view of course, terms and conditions apply etc...)
All in all they had a good time and I got a nice bottle of red wine and a box of chocs as a thank you.
Anyhow, it's one of those bits of Maple I'm starting on, it's not the best half of the log, but I thought I'd jump in get a quick feel of it, so if I got it wrong I'd still have the best bit for another go. I generally work this way, and I often find that the 'best' bit isn't always the best bow.
Here are some pics of it de-barked and roughed out. Being from a bigger diameter log I'll be able to leave the back of the bow as nature created it, using the under bark surface.

Damn!
I was shooting in the Hazel bow some more and I heard a horrible clatter as I shot the nock and cock feather off one of my arrows, known as a 'Robin Hood'.
I'll probably repair it as the bottom of the groove where the string acually bears is still ok.
It was one of ny self nocked arrows too (as opposed to the plastic nock fitted on the other arrow).Shooting 'Primitive' class in NFAS field shoots require the use of self nocked arrows, so I have some of each. plastic is quicker, tougher and easier to replace for general use.

Thursday, 23 August 2012

The Hazel bow has had 110 arrow through it and umpteen coats of Danish oil.
I was just rubbing it over when I noticed an odd mark on the back. There is a couple of tiny pin knots where the grain swells up, they are barely visible and I hadn't allowed any extra thickness there. There was a tiny zigzag line for about 1/4" across the back just to the tip side of the pin knots (It's about 3" from the grip).
From each end of the zigzag there was a hairline going tipwards for about 2". Could it be a splinter trying to lift?

My optimistic self said no, it's just a discolouration of the grain, but my realist gut self said its a damn splinter. I knew the bow was still shooting fine so I winched it back to 28" on the tiller and with my fingernail could just feel the zigzag lifting a tiny amount. I flooded it with low viscosity superglue along the zigzag and the hairline cracks, pulled it to 29" for a split second, then let it down and got the string off quick.
I left it a while and carefully examined the rest of the bow.
On the belly side under the pins was a tiny dark spot of a knot only about 2mm in diameter, I hadn't given it any real thought before. I cleaned it out with a drill bit held in my fingers, it had no strength at all, so I filled it with sawdust/epoxy mix.
I don't know if this contributed to the problem, and I don't know if the problem contributed to the apparent slight change in tiller where I feel the lower limb looked weaker than it did in the pic of it on the tiller.
Anyhow I ran my nice new 12" bastard file over the belly of the upper limb to weaken it a whisker and thus even up the tiller an take a little bit of load off the lower limb. I also ran the file over the outer 2/3 of the back of the lower limb to ease the load off the suspect area.
This tiny amount of work has lost a couple of pounds draw weight and evened the tiller.
I sanded the zigzag and filled knot dead flat then popped it back on the tiller at 28", no sign of the splinter, I shot 10 arrows and it's looking fine.

There is a huge temptation not to post this sort of embarrassing setback, but I think it's a vital part of the blog's usefulness.
The big question is have I fixed it? I'll shoot another 100 arrows through and see how it goes.
The good news is it didn't explode so it was probably a very shallow splinter. If it lifts I could bind it with linen thread rubbed over with epoxy or I could chisel it out into a shallow trench which fades out to nothing at each end and inlay a sliver of hazel. I could bind it anyway as a belt and braces fix. Anyhow, I'll leave it a day or so as I have other stuff to do.

There are often several options and not necessarily just one 'right' one.
I'm a lot happier about it than I was a few hours ago when I first noticed it and you could have knocked me down with a feather.

Monday, 20 August 2012

It needs a few more coats of Danish oil and a nocking point on the string but here are the pics.

I've tuned it up by adjusting the arrow pass and twisting the string up to a 5 1/4" brace as it was slapping my wrist. It shoots really nicely and clocks up 160fps (109 mph) through the chronometer, which makes it my fastest Hazel bow.
It's significantly faster than my old favourite Hazel bow (which has about four fingers of set and is about 5# lower draw weight). But not as fast as Twister (a Yew bow of similar shape and a couple of pounds higher draw weight).

This bow has little set, with the tips pressed against a straight edge I can just get 1 finger between the grip and the straight edge.

The grip has a plaque of bark left on the back which looks good, and the line of pith from the centre of the log is visible on the belly with some of the very subtle grain.

I've shot at least 70 arrows through it and I'm very pleased. The tiller never looks quite the same in the full draw shot as it does on the tiller. It dawns on me that I always take the full draw shot from the same side which shows the bow from the opposite side to how I see it on the tiller, I don't know if that's significant. The tiller is pretty much my usual arc of a circle, but I think maybe it's a tad stiffer in the middle than usual. Maybe I'll post some comparison pics later.

Friday, 17 August 2012

Whew, it's been hot and I've been in and out of the garage working away on the bow.

It's almost there, I've put on horn tip overlays and got the tips nice and skinny and been slowly tillering to even out the limbs and bring the draw length back.

In the pic the lower (left) limb is a hint stiff in it's centre. It's just over 26" draw there and has moved on another inch since then, with the lower limb improved.

I possibly moved onto the file and scraper a bit too early as the progress has been slow, but better slow than sorry. I've been trying to avoid set and get the tiller a bit more elliptical. It's been tricky as over the last 3 or 4 inches of draw the bow is working very hard. I've been easing it off a tad down near the grip as a tiny bit of extra flex there is becomes quite a bit 30" away at the tip. I've been exercising it and shooting a few arrows, which were kicking a bit left and waggling their tails in flight at first until I narrowed the grip.

It's 45# at 27" now and a bit of fiddling, fettling scraping and sanding will get that last inch of draw. The belly is beautifully silky smooth and the bow is looking rather graceful now with a satisfying feel in the hand.

I'll make a proper string tomorrow and shoot it in before any final tweaks to the tiller. After that it's down to an arrow plate, sanding polishing and finishing with Danish oil.

Update:- Saturday, see right, I went for the Waterbuffalo horn tip overlay on a slim tip. It gives a nice contrased when the nock is polished. You can really see the slimmed down shape now. It's gone from ugly ducking to swan. I'll leave that bit of bark on the grip.
I've added another picture of the 2 nocks shown in the previous post, so you can see them from the side.

Thursday, 16 August 2012

Previously I've gone for a wideish tip with a simple shoulder so the string is supported on the edges of the limb or a skinny tip with an overlay so the string is supported by the overlay on the back.

An alternative is the skinny tip somewhere between a pencil and your little finger with a binding round it about half an inch down to support the string, this would have been of sinew and hide glue, but a suitable modern equivalent would be linen thread soaked in epoxy (hide glue goes tacky in hot humid weather). This sort of tip has been found on ancient bows in North America and Europe. The advantage of the skinny tip is the reduced weight, the down side is you have no margin of error for adjusting the string line... mind if the bow is left wide at the grip, then the adjustment can be made there. You can see the difference in tip mass (both Hazel bows), the skinny one on the left is a bit thicker at the tip to maintain rigidity, and you can see how that style evolves into the Mollegabet style (type Mollegabet bow into google images if you don't know what I mean) with a long rigid light tip with the bending part of the limb being the part near the grip. I'm sure that the various styles weren't rigidly defined or categorised like they are today, which is to my mind a nonsense. You hear arguments about "is that a primitive or an American Flatbow?" And one archery society insists a bow can't be an 'English Longbow' unless it has horn nocks!

The bow is still looking a bit chunky, but as I work it down over the next day or so it will hopefully become more elegant.

Last evening I made up a quick jig for supporting one end of a bow when the other is on or in the vice.
I'd seen something similar posted on the Primitive Archer forum and I was getting fed up with resting the bow on the toolbox, or miscellaneous scraps of wood. I can clamp it to the bench wherever is convenient, hopefully it should make things a bit easier.
Update:-
A good days work on it, I've slimmed the tips considerably with the last 6" almost parallel. The reflex has pulled out except near the fades and there is a hint of set mid limb. Overall it's about straight now and pulling 24" at 45#
It's looking much more elegant and I've had a few test shots.

Monday, 13 August 2012

It's coming along nicely. I always say that Hazel is a good wood to have a go with as it's so common.
However there's still a lot of work in making a decent bow.
I've de-crowned it so that I can maintain maximum width and I'm taking care to keep the decrowned surface pretty much following along a ring, nice and flat and parallel to the belly. Holding a couple of arrows across the limb, one pressed against the belly and one against the back is a quick check for parallelism.
An arrow held across each limb also checks the limbs are flat relative to each other.
Not the sort of job you can rush at if you are after perfection, but one that can be acheived with an axe quite quickly to have a go... hmmm that old balance between perfectionism vs utilitarianism.

The sketch below shows how de-crowning reduces thickness substantially whilst retaining width.
The area inside the rectangle represents the cross section of the bow about 1/3 of the way from the grip.
The red dots show where growth rings have been cut, this will give lines running along the length of the bow, so they don't weaken it. (The sketch has been improved from one in an earlier post).
If we remove wood from the belly (lower edge in sketch) instead of de-crowning, to get the same thickness we would have to cut away up to the blue line, which you can see gives a narrower limb.

Thin and wide works well for woods like Hazel as there is less compression stress on the belly.
Imagine a nice thin low stressed bow say 1/4" thick and 1/2" wide, it will be pretty feeble, say 10#. If we make it thicker it will bring up the draw weight but the wood may chrysal. Ah, but if we make two identical bows and stick them side by side, the stress is the same as it was but we have twice the draw weight!
So If we put four such bows side by side we have a bow 1/4" thick 2" wide of 40# draw weigh but no more stressed than the original!

Maybe I'm being a bit fussy with this bow, but I think I'm pushing it quite hard to get a good 45# from this style of bow without recourse to heat treating, which is how I want to do it.
I'm aiming for pretty much a replica of my little Hazel bow but a couple of inches longer, higher draw weight and without the several inches of set which that bow has.
There is often discussion about do you tiller the inner limbs first or the outer limbs. To be honest I think it's a slightly flawed concept, you need to get it all working together to some extent pretty much from first putting a long string on it. Ok you can concentrate on one area, but you must always keep the overall picture in mind. It can be fatal to get sucked into a small area of the bow (say a knot, the grip or the fades) and forget the rest.

The other big problem is, say you work too much on the inner limbs and get the draw too far back, when you then work down the rest of the limb you end up too weak.

Sorry if that's a bit rambling. The real point is, there is no magic recipe or list, do A then B the C and you'll get a bow. It's a bit of everything, slowly homing in on the desired result whilst reacting to what's happening as the work progresses. It has a slight S shaped waggle, I've retained this, as it would have reduced the width to have straightened it out.

Here's a video tour of what it looks like so far, the limbs taper in width from about 2" to 1" and in thickness from about 17mm to 12mm. It pulls back to about a low brace height, and still has it's reflex.

I managed to get a tight string on it which pulls it back to straight, and really shows the string line and the wiggles in the bow. (The stone by the grip shows the arrow pass.)

Saturday, 11 August 2012

This is a long post, so get a mug of tea!
Friday:-
I'm multitasking a bit (Ok I know I'm a bloke, so it's hard to believe) doing a bit with the Oregon Yew billets, preparing them for Bamboo backing.
I've also started on a Hazel primitive for a guy who had a little 35pounder off me a while back and wants one with a bit more thrunge.

Most of it is as twisted as a politicians answer, but one piece is superb.

It has a slight reflex (Most logs dry with a slight reflex when split) and split dead straight.

I've tidied up the split surface to get it clean and flat as I can use that face as a reference to run it through the bandsaw to rough off some of the belly. In the pic on the right you can see the line of pith which runs through the middle of the tree in the centre of the cleaned up face.

I shall maybe jig it up carefully to ensure it runs true, I have got and adjustable vertical guide which I made, but I've learned that the more time spent in preparation the better the result with power tools and it's vital to avoid a costly error or slip which can ruin the wood in the blink of an eye.

That doesn't mean I always do it, as I'm prone to impetuousness.
Whilst cleaning it up I remembered that this is the fatter half of the piece i used to make a bow on a festival day at the club.

This is a good thing as I have experience with the wood already under my belt.

I pressed on and sawed out some of the scrap from the belly of each limb. One limb is pretty close to roughed out dimensions, but the other is a bit oversize.

All the roughing out is aimed at getting it manageable and just flexing, with plenty of width left for shaping and string line correction later. Note the grip is left full width for now. The pic on the right shows the fresh stave with my old fave' Hazel bow, you can see how the colour mellows with time.

Saturday:-

The limbs are nominally 20mm thick at the fade (where it fades into the grip) and 15mm thick at the tip. This give approx 1mm reduction every 6" along the limb. A longbow tapers more like 1.5 - 2mm every 6" but a wide flat bow like this has more width taper and thus needs less thickness taper.

The simplest bow form is a flat limb just tapered in width, even a sheet of hardboard cut to a tapered limb will work as a V low powered kids bow.
I was tempted to reduce the fat limb a bit more on the bandsaw (there was 3-5mm to come off) but I quit while I was ahead and used a spokeshave which was pretty quick and easy.
Power tools can be a snare and a delusion. My view is they don't actually save you time, they save you physical effort. So my view on removing a thin sliver from one limb was that it may cause damage, it will need cleaning up with a spoke shave anyway and it will be V nerve wracking. What could be nicer than sitting outside on a sunny day doing a little spokeshave work with a mug of tea, a piece of toast and the cat on my lap? (Ok I'm lying about the cat)
Enough chat, here are the pics. You see the adjustable jig on the bandsaw, it needs care to ensure the stave is constantly pressed hard up against it. It is positioned a bit in front of the blade, this allows a little side to side movement/adjustment of the stave as the cut progresses, although I had to stop and re-adjust a couple of times too. It's easy to get sort of hypnotised as you are running wood through the band saw, you see it slowly creeping off line and don't stop 'cos you think you can correct it. Whoops, much better to stop adjust and re-start.

Thursday, 9 August 2012

Wednesday Evening:-
The bow was trying it's best to bend sideways.
The two factors contributing to this are the string line being a bit off centre and the cross section being about as thick as it is wide and is some places even thicker! (One of the billets was rather narrow to start with)
I've got it flexing now better now and thinned it a bit ad teased it back to a reasonable brace. The tips are getting pretty narrow where I've tried to adjust the string line. It feels a bit unstable and was making some ominous ticking noises on the tiller, it sounded like cracking glue, but I don't think it's the splice failing.
I'm fully expecting it to explode as it come back further, I think the bug holes in the sap wood will cause it to explode, but you just don't know.
Making a bow is a road travelled in hope rather than certainty.
It's back to about 40# at 21" , I'll be sure to get the video running before I take it back any further.

Thursday Morning:-
Ah the wisdom of sleeping on it!
It doesn't look so bad this morning. I strung it and adjusted the string line a bit more and flexed it a little.
The sideways bend isn't so pronounced, although the whole stave seems to have settled at a slight angle. That is to say if you look at it as a cross section through the grip, it seems to have rotated a few degrees from the expected, but if that's how the wood is balanced then that's fine I'm not going to fight it.
Here's a video of the first real test up on the tiller, it looks surprisingly good.
The right (top) limb is doing most of the bending. Note I've taken the rare precaution of donning a cap and safety glasses, an indicator of my confidence level!
If you look at it full screen you'll see the tape and pencil mark on the scale at 45#, I think the draw is about 22". I went a hint past the 45# but it seemed to get pretty hard. I'll work on the left limb over the course of the day (that's the one with the bug holes) and report back.

I did some work and got it back on the tiller, it was looking good, then BANG. A close examination showed a bug hole right across inside the sapwood where the break is. The video is at the best resolution I can download (slowed down to show it better, but it really needs a high speed camera to actually see it fail).

Here's a pic of the break in the sapwood you can see the curve of the bug hole along the break and a neat round hole where it turns down into the wood...

I've run the next two billets through the bandsaw to take off the sapwood, but I may need to buy (wince) a bench mounted belt sander/linisher to thin down the bamboo I'm going to use for a backing.

Just noticed someone has ticked the 'boring' reactions box... LOL! Maybe they need to have a bow explode above their head to see how boring it is?

Monday, 6 August 2012

I mentioned how adding a riser section changes the bow geometry in an earlier post, here's an attempt at a 'proof'
The diagram is just the top half of the bow, I'm assuming its lower half is completely symmetrical.

The black limbs at the top represent the upper limb of a bow at brace and full draw.(BOW 1)
The string is length L. and the full draw length is at B (On the big fat red horizontal centre line).
If we now extend the limb downwards into a rigid riser section, also of length L (BOW 2), we see the string is now length 2L. The limb bends exactly as it did before to point A (not strictly true, due to the slight change of string angle, but this is my simplified model)
Now drawing an arc for the string of radius 2L centred on point A, we see it intersects the new horizontal centre line at point D which is our new draw length.
So you can see it is drawing further.
If the limbs return to brace at the same time, then the arrow is travelling further in the same time and is thus faster!
Blimey, my brain hurts now.

Sunday, 5 August 2012

Splicing is easy in theory, mark out a paper template, cut it out, stick it on the wood, saw it out, glue it together.

The reality is trickier unless you are working with machined timber.

I cut out a template, but when stuck onto the undulating back of the billet it distorts.
It's also tricky to hold the billet dead flat against the bed of the bandsaw to ensure a vertical cut, but on one half I had stuck an off cut of 1/4" MDF board onto the belly of the billet, this was a great help in running it through and it also allowed me to adjust the angle of the save by slipping in scraps of wood while the 10 minute epoxy was hardening prior to sawing.

It's just a shame I didn't do the same on the other billet, as it came out with the taper slightly wedge shaped when viewed from the end (like looking at the prow of a ship). I had to do a fair bit of painstaking work with rasp and sanding block to get a good fit, which I checked by dry fitting it and looking for gaps with the bench light shining behind.
It was glued last evening and left overnight. I've cleaned it up this morning and it looks good, the alignment is a tad out which is slightly tricky as one of the billets was V narrow to start with. It should be ok, and where the centre line is biased to one side, I can make that side the arrow pass (back to that old question 'can a longbow be right handed?).

Here's a load of pics.
One shows the few bug holes in the sapwood which I shall keep an eye on as I rough out the bow, hopefully they don't go deep. Before flexing the bow, I shall run low viscosity superglue into them.
This is all a bit of an experiment really and if it blows up on me I'll back the any future bows from this batch of wood (prob' with bamboo).

There is some nice character in these billets and you can see a sort of dip/twist thing going on.

Other pics shows the centre line alignment and a mug of tea.

Talking of bamboo there are some silly urban myths about it.
One:- Because it's a grass it keep growing after it's cut... hmmm, yes maybe the bit in the ground does, I don't know. But that's not the bit we use! Do the grass cuttings on your compost heap keep growing? No they don't.
Next!
Two:- It's not a 'legitimate' bow wood because it's not a wood it's a grass.
Tell that to the Japanese who for centuries have made their bows from it, not to mention the countless other peoples who make bows from other non-wood materials, horn, sinew and bone.
The view that it's not a legitimate wood is promulgated by a bowyer who is keen to stir up controversy and get his name out there, after all, it's free publicity, and he has to make a living and pay his overheads.
However I shan't mention his name as I have no wish to give him even more!
Ah, I feel better for that rant, time for another cup of tea.

Drat, just set up my shave horse outside and started cleaning it up with my spokeshave and the thunder and rain came on. S'pose I'll watch the Olympics...

Friday, 3 August 2012

I've been busy decorating for the last week, but I've finished now and musing as to what to pick up next. I'd promised a guy I'd try to do a primitive for him. He's quite interested in the Hornbeam one I recently finished so I looked it over, cleaned up the arrow pass a bit to make it closer to centre shot and tried a couple of arrows. It felt good and the second shot skewered the 2x2" scrap of white pvc foam I was aiming at from 10 yards.
I set up the chronometer and it registered a respectable 139fps.
I looked at some Yew I have lying around and then though i should check the Oregon Yew again, the bug holes are still there, but a couple of skinny billets might make a longbow, I'm thinking maybe a flight bow with a slightly more 'elliptical' tiller.
I'm a bit ambivalent about the term 'elliptical' as I'm not sure exactly what is meant, does it mean simply a section of an ellipse, or I suspect it may mean an two arcs of a circle but separated by a stiff handle section of about 15", or is it just a slightly whip ended bow?
The geometry of a bow is quite complex.
If you take two rigid limbs (say 25" or so long) pivoted at the centre joined with a string and allow them to hinge back say 45 degrees, the string will come back say 20". If you now re draw the same set up with a rigid section of 15" between the two limbs making the bow longer. You now find that as the limbs come back to 45 degrees the string now draws back further!
So, in this simplified model, if the limb tips return to their rest position in the same time as they did in the first example the arrow will be travelling further in the same time, or, as we sometimes call it, faster!
Anyhow I've started marking up the two billets for splicing together.
Doubtless some pics later in the weekend.
Hmmm. Just noticed the 'explain more' so I tried to draw a diagram to show my simplified model of a bow and how a riser section effect the draw. Drat, it seemed to show the opposite conclusion! Arrrggghh, so I'm going to have to pore over the maths/geometry for some time, which isn't my fave thing, but having done it once it's wound me up!